2001 v8 PCM, how to diagnose it as culprit of bad shifting?

[fabrizio]

Hi,

I took out the PCM for visual inspection,there are some photos.

My car is experiencing a bad shifting I think all gears, it takes too long to shift and it revs up, before shiftting it feels loose ,like not engaging or going in Neutral until it bangs(kick)

It was working great after rebuild(bands/transgo shift kit /new OD servo/servo bore fix) shifting flawless for months.(now has been 8 months at garage)

2001 V8
NO CODES
Reverse ok
Drive OK
It had a little bang between P and D vice versa but not a delay​

I'm checking if could be the solenoid pack or the PCM.
I have no Codes so I have no idea :/

How can i diagnosed a bad PCB?

-After my research I tought it was something with a fried microcontroller or memory but No, it's a driver(transistor/mosfet, maybe some buffer circuits) in short or open state.

-I saw another case when they replaced the solenoid pack and still shifting bad,the Pressure Control Solenoid where involved, the scanner read 1A current and the digital multimeter read(physically connected) 0.5A so the signal was poor as the functionality. So in this case it is a driver PCM fault.

How a bad Coil On plug can damage the PCM?

-Well , the coil is driven by a mosfet transistor,this transistor has some specs as Max voltage,current, if a bad coil generate large voltage spikes and they reach the transistor Breaking Voltage for long period of time,bye bye , or even if the current is not limited, bye bye transistor.

-If a solenoid is in short circuit it will demand more current if not limited and again,bbye bye transistor.

The solenoid pack contains the Shift Solenoids A.B.C.D. and the Pressure control Solenoids A.B.C
I did a resistance test measuring the solenoid coils, all are ok so I can discard an open/shorted solenoid coils.

But it could be stuck, right?​

Shifting so slowly could be a Pressure control solenoid?

If I do a pressure test at Pressure Control PORT A,B or C Could this guide me find the component fail?

Too many questions , Just to share and learn

Feel free to ask and suggest,

Thanks for helping

**Damm I mis my car .
How to show full size pictures? :?

 

[joegr]

You are not going to be able to see the damage without depotting the transistors and using a microscope. They don't fail completely. That would be easy to diagnose and would throw codes. Instead, they become marginal. There is a test mode (PCM installed) that you can use to get the PCM to output a specific amount of current to each solenoid. You measure that current, and if it is wrong you have found the problem.

As a practical matter, you already have the PCM out, so send it in for testing and repair.

 

[fabrizio]

You're right Joegr,

Some times the mosfet get marginal and does not show bad symtoms as shorted or open until current is demanded.

I did a test measuring the current to PCS A,B and C. This was to verify if the transistor source the current as the PCM thinks is sourcing.

*Forscan BT / Android phone DMM fluke 87V

I turn ON the car an let the engine OFF, I move shift lever P,R,N,D , SST 2-3

I connected the dmm in series to the wire to measure(cutting wire, I have no clamp-on meter).

Thea readings :

Pressure Control Solenoid - Scanner - DMM (shift lever P position)

PCS A - 0.93A - 0.942A ( OK )
PCS B - 0.54A - 0.539A ( OK )
PCS C - 0.93A - 0.933A ( OK )
​

I moved the shift lever P,R,N,D , SST 2-3 , i could hear some clickings, the values reads on scanner were the same on the DMM too.

How is the test your talking about? Increasgin the PCS and measuring the current?

I know it could be easier to send the PCM and wait for repair but I would like to be sure, as you know I'm in Mexico and I have to pay almost the double for every part. Even if the PCM were OK I should to pay $ 200.

really aprecciate every suggestion ,thank you.

Best regards Fabrizio

 

[fabrizio]

Just for information some pcm parts.

 

[cubanocelso]

In case you have to change the ECU this baby has to go 2001 lincoln ls 316000 miles.
This is the ebay link only we would have to see the shipping price.
2001 lincoln ls pcm ecu 3.9 v8 | eBay
Anyway I go to Laredo TX every week I guess sending it from there will not be very expensive.
Good Luck

 

[fabrizio]

Hi, this video is really helpfull.

Separeting the problem , TCM(transmision control module,we know it as PCM on our cars), valvebody or solenoid pack.



link hxxps://youtu.be/t00XVU7YUxI

 

[RigsLS]

Always nice to see the conformal coating on those bad boys.

 

[RigsLS]

fabrizio,

do you still have your PCM out?

can you confirm the following,

The keypad can be operated with the factory set 5–digit entry code; this code is located on the owner’s wallet card in the glove box, is marked on the computer module, and is available from your authorized dealer. You can also create your own 5–digit personal entry code.


Do you see a five digit code marked on the exterior of your PCM somewhere ?????
~ always understood as having to go to the Dealership to obtain door pad entry code, OM says it's supposed to be marked on the computer module. I'd imagine they are referring to the PCM.

Rather interesting if true.
.

 

[joegr]

The "computer module" they are talking about is the DDM (Driver's Door Module), not the PCM (Powertrain Control Module). The DDM is the module that the keypad is attached to and it stores the factory code and the user codes. It also memorizes the remotes. The PCM is not involved in this at all. Note that there are several "computer" modules in the LS.

I know my factory codes (I have the cards with the codes for both LSes). I have looked at the DDM in at least one of them, and I couldn't find the code anywhere on the outside of the module. I suspect that the practice of putting the code there was changed, but the manuals were not updated.

 

[fabrizio]

I have some pictures, let me go home and I'll upload them.
There's some numbers, I think is the VIN/part number.

My car does not have keypad.

 

[RigsLS]

No key pad, no sense.